Video Transcript
A sample is tested with iodine. What is the color change that will
occur if the sample contains starch? (A) Blue-black to brown. (B) Pale blue to purple. (C) Brown to brick-red. (D) Brown to blue-black. Or (E) brown to cloudy white
precipitate.
As the question suggests, the food
test we use to see if a sample of food contains starch is the iodine test. For example, let’s say we want to
determine if this food contains starch. We could add a few drops of iodine
solution to this sample of food. This can be done in a dish or in a
test tube.
In its liquid form, iodine is
usually a light orange to brown color. However, when iodine solution comes
into contact with starch, it will turn very dark brown, blue-black, or black. This is known as a positive result
because it shows the food contains starch. If there is no color change, it is
a negative result, meaning there is no starch present in the food.
So the correct answer to this
question is (D). The iodine color change that will
occur if the sample contains starch is from brown to blue-black.
